The present invention relates to an image forming apparatus provided with a resin frame made of resin and image forming units.
A frame that constitutes the basic structure of an image forming apparatus such as a copying machine, a printer, a facsimile machine or a digital multifunction machine is conventionally a metal frame structure made by assembling pressed metal parts or metal based steel materials by joining or welding.
In a recent trend of reducing the production cost of image forming apparatuses, those produced with conventional metal frames are not sufficiently profitable. Moreover, there is a great demand for compactness and lightness of weight, which requires simplicity of structures and reduction of the number of parts. However, there is a limit in compactness and lightness of metal frame structures.
Resin frames made of resin may be adopted in view of cost reduction, compactness and lightness of weight required for frame structures, but in this case there may be problems in terms of strength.
For an image forming apparatus provided with image forming units (process units) including a photosensitive unit, a charging unit and a development unit, ducts may be provided for the purpose of exhausting unwanted substances such as ozone or nitrogen oxides (NOx) generated by a charger that charges a photosensitive member to a predetermined potential, or cooling the image forming units.
For example, JP 2009-122221A (Patent Document 1) discloses an image forming apparatus that can exhaust ozone without increasing the size of the apparatus by providing a duct member for allowing air to flow on the removable side of the image forming units integrally with a positioning member for a photosensitive member that positions the rotation axis of the photosensitive member, and allowing air near a charger to flow in from an opening portion provided between the positioning member for the photosensitive member and the duct member into the duct by means of a fan that generates air flow.
However, in the image forming apparatuses disclosed in Patent Document 1, the duct member allows air to flow only on the removable side of the image forming units, and air cannot reliably flow in the image forming units, and thus unwanted substances cannot be exhausted reliably or the image forming units cannot be cooled reliably. Furthermore, although Patent Document 1 does not disclose that the frame is made of metal or resin, if the frame of the image forming apparatus of Patent Document 1 is made of resin, the duct member cannot contribute to reinforcement of the frame, which does not provide any solution to the strength problem.